Kurt,
Do not be in too much of a hurry to toss out those black palstic grips. You might have a real pair made by Mauser which have been called "Black Widow" grips by some for marketing purposes.
If you post good close-up photos of your grips (both front and back views) the folks here could advise you if they are real or "repros". Real ones have been selling on e-Bay in the $ 150-180 price range...
Regards,
Pete... <img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" />